1. Field of the Invention
The present invention relates to a method for displaying images on a plasma display. More particularly, the present invention relates to a method for reducing dynamic false contour on a plasma display.
2. Description of the Related Art
Plasma display panels (PDP) utilize electron discharge of inert gases to produce ultraviolet rays to excite red, green and blue fluorescent powder in order to display images consisting of colored pixels. The appearance of PDP has a tremendous impact to the market of medium-sized and large-sized (about 40 to 70 inches) display. A plasma display is far thinner and lighter than a traditional cathode-ray tube (CRT) television. A plasma display is proof against magnetic field and also has many advantages, such as digital architecture, high resolution, wide viewing angels and flat display surface, which satisfies the requirements of small size and light weight of modern multimedia devices.
However, a problem called dynamic false contour usually happens when a PDP is displaying a dynamic image. A traditional solution is using two different grayscale phases, such as phases A and B, as depicted in FIGS. 1A and 1B. FIG. 1A illustrates phases A and B interweaved in a chess board pattern in the same frame field. FIG. 1B illustrates how phases A and B are interleaved in consecutive frame fields. Each cell of the matrices in FIG. 1A and FIG. 1B represents a pixel, such as the pixel P in FIG. 1A. “A” and “B” in FIGS. 1A and 1B are two different grayscale phases corresponding to the same grayscale value. For example, to implement the grayscale value of 64, 64 pulses are applied successively in phase A, while two batches of 32 pulses each are applied in phase B. Such solution in FIGS. 1A and 1B utilize interleaved phases. The phases are interleaved both spatially and temporally. That is, phases A and B are interleaved among the pixels in the same frame field, both horizontally and vertically (FIG. 1A), and are also interleaved between consecutive frame fields (FIG. 1B). The gray scale phases A and B are allocated in this way to evenly distribute visual focus. The dynamic false contours are therefore effectively reduced.
FIGS. 1A and 1B proposed a solution for reducing the dynamic false contour. However, during the development of a plasma display, test patterns are often used to test and verify whether the plasma display functions properly. The pixel lattice pattern, as shown in FIG. 2, is one of such test patterns. Each cell of the matrix in FIG. 2 represents a pixel. As can be seen in FIG. 2, in the pixel lattice pattern, all pixels immediately adjacent to an active pixel are inactive. The problem of flickering is especially obvious when the pixel lattice pattern is being displayed.
The reason why the problem of flickering is especially obvious when the pixel lattice pattern is being displayed is that there is a chance for the pixel lattice pattern to be synchronous with the interleave of the phases A and B. FIGS. 3A˜3C illustrate the situation in which the pixel lattice pattern is synchronous with the interleave of the phases A and B. Each cell of the matrices in FIGS. 3A˜3C represents a pixel. Please refer to FIGS. 3A˜3C in the following discussions. FIG. 3A illustrates the first frame field, in which the pixel lattice pattern happens to be synchronous with phase A. FIG. 3B illustrates the second frame field, in which the pixel lattice pattern happens to be synchronous with phase B. And FIG. 3C illustrates successive frame fields which display the pixel lattice pattern and adopt the interleaved phases simultaneously. Due to the structure of the pixel lattice pattern, the active pixels in the first frame field are all in phase A, whereas the active pixels in the second frame field are all in phase B, and so on. Such a repeated occurrence is the major cause of the flickering problem.